Rashi on Numbers 7:22/רש"י על במדבר ז׳:כ״ב

1שעיר עזים [ONE] KID OF THE GOATS — in order to make expiation for the “selling of Joseph” with reference to whom it states, (Genesis 37:31) “and they slaughtered a kid of the goats” (Numbers Rabbah 13:13).